Method and system for providing multiple views directed to multiple viewing zones

ABSTRACT

A multi view display ( 49 ) is arranged to provide large viewing zones ( 23, 24 ) while producing little or no cross-talk The display may include a barrier ( 20 ) comprising a plurality of color portions ( 20   a   , 20   b   , 20   c ) that co-operate with color filters ( 19   a-   19   f ) in a display panel ( 14 ) to selectively direct light to the viewing zones ( 23, 24 ) A lenticular screen ( 30 ) may be arranged to create or image light lines onto imaging units ( 32   a   , 32   f ) of the display panel ( 14 ) that are spaced from one another, so that adjacent units ( 32   a   , 32   f ) are illuminated by light from different lenses ( 30   a   , 30   b   , 30   c ), directed towards different viewing zones ( 23, 24 ) A light source ( 35 ) may generate the light at positions aligned with boundaries between adjacent lenses ( 30   a   , 30   b,    30   c ) The imaging units may be operated so that units ( 32   a,    32   b ) displaying information for the first viewing zone ( 23 ) are separated from units ( 32   d   , 32   e ) displaying information for the second viewing zone ( 24 ) by units ( 32   c   , 32   f ) not used to display information Adjacent columns of units ( 32   a   , 32   b ) may be used to display information to one viewing zone ( 23 ) The viewing zones ( 23, 24 ) may be enlarged using a scatterer ( 36 ) A switchable diffuser ( 40 ) or barrier ( 48 ) may be provided so that the display ( 49 ) can operate in different multi-view and/or single view modes.

The present invention relates to display devices arranged to providemultiple views.

A multi-view display may be arranged to present different information totwo or more users. FIG. 1 depicts an arrangement in which two views arecreated by a conventional multi-view display device 1. Such a display 1may provided in the dashboard area of an automotive vehicle and arrangedto present a route planner to the driver 2, while displaying emailmessages or images from a digital versatile disc (DVD) to one or morepassengers 3. The route planner will be visible to the driver 2 if he orshe is positioned in a first viewing zone 4, while the passenger 3 canview their information when positioned in a second viewing zone 5.

In the arrangement of FIG. 1, a region 6 is located in between theviewing zones 4, 5, in which both sets of information, that is, theinformation for display to the driver 2 and information intended for thepassenger 3, are visible simultaneously. In other words, in region 6,there is cross-talk between the information displayed in viewing zone 4and in viewing zone 5. In known multi-view displays, the sizes of theviewing zones 4, 5 are relatively small when compared with the size ofthe cross-talk region 6. Typically, the opening angles ? of the viewingzones 4, 5 are about 10°. This restricts the positions in which thedriver 2 and passenger 3 can view information. In addition, it increasesthe probability that the driver 2 or passenger 3 will move into aposition in the cross-talk region 6.

For an automotive application, the presence of a cross-talk region 6 isparticularly undesirable, since a passenger 7 sitting in the middle of arear bank of seats may be located in this region 6 and be presented withconfusing information. Furthermore, for safety reasons, the display 1should prevent the driver 2 from seeing the information presented to thepassenger. Therefore, the viewing zones 4, 5 should be physicallyseparate and cross-talk in region 6 minimised.

Conventional methods for creating multiple views are based on similarprinciples to those used in auto-stereoscopic 3D displays, in whichdifferent information is directed to left and right eyes of a viewer. Inone prior technique, a lenticular screen 8 is placed in front of adisplay panel 9, such as a liquid crystal display (LCD), as shown inFIG. 2. The display produces two views 10, 11. Presently available LCDdevices have a glass thickness t of 0.7 or 1.1 mm in order to createlarge viewing angles. A multi-view display based on the arrangement ofFIG. 2 is not feasible with such thicknesses. For example, if a displayhas a subpixel pitch p of 0.042 mm, the light rays emerging from twoadjacent subpixels 9 a, 9 b will be separated by an angle of 4°,irrespective of the strength of the lenses in the lenticular screen 8.This separation is insufficient for a multi-view display. In addition,this type of display creates a cross-talk region that is large incomparison to the viewing zones.

Another conventional method utilises a front barrier 12, positioned infront of the display panel 9, as shown in FIG. 3. The barrier 12 has aplurality of slits 13 that allow light from the display panel 9 to passthrough, creating viewing zones 4, 5 and a significantly largercross-talk region 6. The sizes of the viewing zones 4, 5 depend on thetransmission of the barrier 12. For example, if the transmission of thebarrier 11 is close to zero, that is, if the zslits 13 are of minimalwidth, the viewing zones 4, 5 have opening angles ? of approximately40°. However, if the transmission of the barrier 11 is 25%, the openingangles ? are reduced to approximately 100 and the cross-talk region 6 isconsiderably larger, having an opening angle ?′ of approximately 20°.Therefore, in order to produce large viewing zones 4, 5, thetransmission of the barrier 12 must be restricted. However, this type ofarrangement suffers from poor light efficiency, even when a barrier 12with a high transmission is used, as a considerable portion of the lightemerging from the display panel 9 is blocked.

Another known technique, not depicted, uses a rear barrier, whichcomprises a plurality of slits and is positioned between the backlightand display panel. This arrangement produces considerable cross-talk dueto the finite width of the slits. As discussed in relation to thebarrier arrangement of FIG. 3, cross-talk can be reduced by decreasingthe width of the slits but this reduces the light efficiency of thedisplay.

In order to create two views that are well separated, at angles of, say,±30° from normal the separation between the rear barrier and displaypanel should be less than p/0.3536, where p is the pitch of thesubpixels of the display panel. The separation is usually provided by anintervening sheet of glass. However, as typical subpixel sizes arearound 99 μm, this would require a sheet of glass of thickness 280 μm,which is presently unfeasible.

In summary, presently known multi-view display techniques provideviewing zones 4, 5 of limited size, separated by one or more relativelylarge regions 6 in which there is cross-talk. It is an object of thepresent to provide a multi-view display that creates two or more viewingzones that are relatively large when compared with prior art displays,in which cross-talk is either avoided or restricted to a relativelysmall region.

According to a first aspect of the invention, a multi-view displayconfigured to display two or more views directed to two or morerespective viewing zones comprises a display panel, comprising aplurality of imaging units and a plurality of colour filters, whereineach of said colour filters is associated with one of said imagingunits, the colour filters being arranged according to a first pitch andin a first sequence of colours, and a barrier including a plurality ofcolour portions comprising colour filter material, the colour portionsbeing arranged according to a second pitch that is substantially equalto twice the first pitch and in a second sequence of colours thatcorresponds to the first sequence of colours when reversed in order,wherein the barrier is positioned so that light exits the display panelafter passing through one colour portion and one of said colour filtersand the colour portions of the barrier are configured to cooperate withthe colour filters to selectively direct said light to the first andsecond viewing zones.

The imaging units may be pixels or subpixels or groups thereof.

The second pitch may vary slightly from a value that is twice the firstpitch, for example, in order to provide a view point correction or toimprove separation between the viewing zones.

The colour portions are arranged in a colour sequence that is reversedwith respect to the colour sequence of the colour filters and colourportions are arranged in colour sequences that are reversed with respectto one another. For example, the colour filters may be arranged in aperiodic sequence of red, green and blue filters, while the colourportions are arranged in a second periodic sequence of blue, green andred filters.

The colour barrier may be positioned in front of the imaging units, withrespect to a viewer, so that light passes through the colour filtersbefore passing through the barrier. Alternatively, the colour barriermay be a rear barrier, positioned behind the imaging units, in whichcase the colour portions may comprise cholesteric filter material.

The multi-view display may comprise a light source arranged to providebacklighting for the imaging units of the display panel. The lightsource may comprises a plurality of light emitting diodes, wherein atleast two of said light emitting diodes are configured to emit light offirst and second colours respectively, in order to facilitate selectivetransmission of light through the barrier and the colour filtersaccording to colour. Alternatively, where the colour barrier is placedin front of the imaging units, the imaging units may comprise lightemissive devices.

The colour portions of the barrier and/or the colour filters may beseparated from one another by black matrices.

The colour portions and colour filters may be aligned so that theviewing zones produced by the display are asymmetrically arranged.

This aspect also provides a display system comprising the multi-viewdisplay and audio output means arranged to output audio signalscorresponding to the information displayed in one or more of saidviewing zones.

The display or display system according to this aspect may be arrangedto display information to viewers in an automotive vehicle.

According to a second aspect of the invention, a method of manufacturinga multi-view display according to the first aspect of the invention,arranged so that the colour barrier is positioned so that light passesthrough the colour filters before passing through the barrier, comprisesproviding a plurality of colour portions on a light transmissivesubstrate, placing a sheet of light transmissive material over saidplurality of colour portions and providing the plurality of colourfilters of the display panel on said sheet of light transmissivematerial.

According to a third aspect of the invention, a method of manufacturinga multi-view display according to the first aspect of the invention,arranged so that the colour barrier is positioned so that light passesthrough the colour portions before passing through the colour filters,comprises providing said plurality of colour portions on a lighttransmissive substrate, placing a sheet of light transmissive materialover said plurality of colour portions and providing means configured tocontrol said imaging units on said sheet.

In a multi-view display manufactured according to the methods of thesecond and third aspects, a separation between the colour barrier andthe imaging units is determined by the thickness of the sheet. Thisthickness may be less than that of a typical substrate of a liquidcrystal device. The reduction in this separation may contribute to anincrease in the sizes of the viewing zones created by the display whencompared with prior art arrangements.

According to a fourth aspect of the invention, a multi-view displaycomprises a display panel, comprising a plurality of imaging unitsconfigured with a first pitch, a light source arranged to illuminate thedisplay panel and a lenticular screen arranged to focus light emitted bythe light source to create images of light lines at said plurality ofimaging units, the lenticular screen comprising a plurality of lensesconfigured with a second pitch, wherein said second pitch issubstantially equal to an integer multiple of said first pitch, so thatsaid lenses create images on two of said imaging units that are spacedapart from one another and adjacent imaging units are illuminated byimages created by different lenses.

The light source may be arranged to generate the light lines atpositions arranged according to a third pitch, wherein the third pitchis substantially equal to the second pitch. The positions may be alignedwith boundaries between adjacent ones of said lenses.

According to a fifth aspect of the invention, a multi-view displaycomprises a display panel comprising a plurality of imaging unitsconfigured with a first pitch, a light source arranged to generate aplurality of light lines at a plurality of positions arranged with asecond pitch and a lenticular screen arranged to focus light emitted bythe light source to create images of light lines at said plurality ofimaging units, the lenticular screen comprising a plurality of lensesconfigured with a third pitch that is substantially equal to the secondpitch and arranged so that boundaries between adjacent lenses arealigned with the positions at which the light lines, are generatedwherein said second pitch is substantially equal to an integer multipleof said first pitch, so that said lenses create images on two of saidimaging units that are spaced apart from one another and adjacentimaging units are illuminated by images created by different lenses.

A multi-view display according to the fourth or fifth aspects maycomprise a scatterer arranged to scatter light output by the displaypanel, to provide a further increase in the sizes of the viewing zones.The scatterer may be a controlled scatterer with a predeterminedscattering profile. For example, the scatterer may have a scatteringsurface comprising periodic structural features.

A multi-view display according to the fourth or fifth aspects maycomprise a switchable diffuser and mode switching means configured toswitch said diffuser between a diffusive state and a light transmissivestate, wherein said diffuser is positioned between the light source andimaging units so that, when the diffuser is in its light transmissivestate, the light lines are imaged at the imaging units and, when thediffuser is in its diffusive state, the imaging units are provided withsubstantially uniform illumination. This permits the display to beswitched into a first mode in which the display creates multiple viewsand a second mode in which the display presents a single view.

The diffuser may be configured to switch between these states inresponse to the application or removal of an electric field by the modeswitching means.

A multi-view display according to the fourth or fifth aspects may beincluded in a display system, together with audio output means arrangedto output audio signals corresponding to the information displayed inone or more of said viewing zones.

According to a sixth aspect of the invention, a multi-view displaycomprises a display panel, comprising a first plurality of imaging unitsarranged to display a first view to a first viewing zone and a pluralityof second imaging units arranged to display a second view to a secondviewing zone, said first imaging units and second imaging units beingseparated by a plurality of third imaging units, and an illuminationarrangement configured to illuminate the display panel with a pluralityof light lines, the display being arranged such that said third imagingunits are not used to display information when said first and secondviews are displayed.

In this manner, the imaging units effectively act as a barrier fordirecting light towards the viewing zones.

The third imaging units may be switched off when said first and secondviews are displayed.

The first, second and third pluralities of imaging units may be arrangedin columns to form part of a two dimensional array of imaging units. Theplurality of first imaging units may comprise imaging units arranged inadjacent columns of the array. Similarly, the plurality of secondimaging units comprises imaging units may be arranged in adjacentcolumns of the display panel. The first, second and third pluralities ofimaging units may be arranged in a periodic sequence of columns in saidarray.

The display panel may comprise a plurality of filters arranged in alayout that departs from a conventional periodic sequence of columns offilters corresponding to three primary colours. For example, the filtersmay be arranged in a two-dimensional array and/or may be based on fouror more primary colours.

The illumination arrangement may comprise a light source and a barrierincluding a plurality of light transmissive portions arranged at a givenpitch, located between the light source and the display panel, so thatthe display panel is illuminated by a plurality of light lines. Themulti-view display may comprise a barrier including a plurality of lighttransmissive portions, to selectively admit light, said lighttransmissive portions being arranged at a first pitch and the barrierbeing positioned so that light emerging from the imaging units isincident thereon.

Where a barrier is provided, it may be in the form of a switchabledevice, such as a liquid crystal cell, that can be switched between aselectively transmissive mode, in which the barrier selectively admitslight, and a light transmissive mode, in which the barrier issubstantially light transmissive in order to provide uniformillumination for the display panel. This allows the display to beoperated in both multi-view and single-view modes. Alternatively, oradditionally, the barrier may be a switchable device, such as a liquidcrystal cell, that can be operated in a first mode, in which the lighttransmissive portions are arranged with the first pitch, and a secondmode, in which the light transmissive portions are arranged with asecond pitch.

The display panel may comprise a plurality of colour filters. The colourfilters and the barrier may be arranged so that they are out ofalignment with each other. In other words, the barrier may be slantedwith respect to the colour filters. Such an arrangement may be used toovercome an incompatibility between the arrangement of the first and/orsecond imaging units and the arrangement of the colour filters.

The illumination arrangement may comprise a light source arranged togenerate light lines and a lenticular screen arranged to image the lightlines within the display panel.

Light transmissive portions of the barrier and the third imaging unitsare aligned such that the light output by display panel creates theviewing zones in an asymmetrical arrangement.

The multi-view display may be arranged to display information in anautomotive vehicle.

This aspect also provides a display system comprising the multi-viewdisplay and audio output means arranged to output audio signalscorresponding to the information displayed in one or more of saidviewing zones.

The invention will be described in detail by way of example embodiments,with reference to the following drawings, in which:

FIG. 1 depicts viewing zones and a cross-talk region created by aconventional multi-view display;

FIG. 2 depicts a known multi-view display comprising a lenticularscreen;

FIG. 3 depicts another known multi-view display, which comprises a frontbarrier;

FIG. 4 depicts a multi-view display according to a first embodiment ofthe invention;

FIG. 5 is a plan view of a barrier of the multi-view display of FIG. 4;

FIG. 6 is an enlarged view of part of the multi-view display of FIG. 4;

FIG. 7 is a plan view of a barrier used in a multi-view displayaccording to a second embodiment of the invention;

FIG. 8 is an enlarged view of part of a multi-view display according tothe second embodiment of the invention;

FIG. 9 is a graph showing the extent of the viewing zones as a functionof the transmission of a barrier in the multi-view display of FIG. 4;

FIG. 10 is a graph showing the extent of the viewing zones as a functionof the distance between the barrier and an imaging device for themulti-view display of FIG. 4;

FIG. 11 depicts part of a multi-view display according to a thirdembodiment of the invention;

FIG. 12 depicts part of a multi-view display according to a fourthembodiment of the invention; FIG. 13 depicts a multi-view displayaccording to a fifth embodiment of the invention;

FIG. 14 depicts the filter layer of a display panel in the display ofFIG. 13;

FIG. 15 shows a multi-view display according to a sixth embodiment ofthe invention;

FIG. 16 depicts the path of light rays passing through the display ofFIG. 15;

FIG. 17 depicts of a multi-view display according to a seventhembodiment of the invention;

FIGS. 18 a and 18 b show the scattering profile of a normal scattererand a controlled scatterer used in the multi-view display of FIG. 16;

FIGS. 19 a and 19 b depicts surfaces of suitable controlled scatterersfor use in the multi-view display of FIG. 16;

FIG. 20 depicts a multi-view display according to an eighth embodimentof the invention;

FIG. 21 depicts an array of subpixels for use in a multi-view displayaccording to a ninth embodiment of the invention;

FIG. 22 depicts a multi-view display according to the ninth embodimentof the invention;

FIG. 23 is a graph showing the relationship between the angles at whichan overlap zone begins and ends and the dimensions of the multi-viewdisplay of FIG. 22;

FIG. 24 depicts a multi-view display according to a tenth embodiment ofthe invention;

FIG. 25 depicts a multi-view display according to an eleventh embodimentof the invention;

FIG. 26 depicts the imaging of stray light in the multi-view display ofFIG. 25;

FIG. 27 depicts an array of subpixels for use in a multi-view displayaccording to a twelfth embodiment of the invention;

FIG. 28 depicts a multi-view display according to the twelfth embodimentof the invention;

FIG. 29 depicts an array of subpixels for use in a multi-view displayaccording to a thirteenth embodiment of the invention;

FIG. 30 depicts a multi-view display according to a fourteenthembodiment of the invention;

FIG. 31 depicts a multi-view display according to a fifteenth embodimentof the invention;

FIG. 32 shows a display system comprising a multi-view display accordingto any one of the first to fifteenth embodiments;

FIG. 33 depicts an automotive vehicle equipped with the display systemof FIG. 32; and

FIG. 34 depicts another display system comprising a multi-view displayaccording to any one of the first to fifteenth embodiments.

Referring to FIG. 4, a multi-view display according to a firstembodiment of the invention comprises a display panel 14 and a backlight15.

In this example, the display panel 14 comprises a layer 16 ofelectro-optically active material, such as a liquid crystal material,sandwiched between two light-transmissive substrates 17, 18. Thesubstrates 17, 18 may be formed from glass or another suitable lighttransmissive material such as a plastic or quartz. Where liquid crystalmaterial is used, the operation of the layer 16 may be based on any oneof a twisted nematic (TN), super-twisted nematic (STN), verticallyaligned nematic (VAN), optically compensated birefringence (OCB),in-plane switching nematics (IPS) or ferro-electric effect formodulating a polarisation direction of incident light.

The display panel 14 is divided into an array of subpixels and isprovided with an active matrix or a passive matrix arrangement (notshown) for driving the array in order to allow an image to be displayed,in a manner well known per se.

A filter layer 19 is provided, comprising a series of columns of red,green and blue filters extending across the display in a verticaldirection. The filters determine the colour of the subpixels when seenby a viewer. Each filter in the filter layer 19 is separated itsadjacent filters by a black matrix. In FIG. 4, and in subsequentfigures, red, green and blue filters are indicated using lines, shadingand hatching respectively, while the black matrix is shown using solidshading.

In front of the filter layer 19, there is provided a barrier 20. Thebarrier 20 is located on the substrate 17 and is separated from thefilter layer 19 by a sheet 21 of glass or other suitable lighttransmissive material.

The barrier 20, which is shown in plan view in FIG. 5, comprises aseries of columns of red, blue and green colour filters separated by ablack matrix 22. The colour filters are arranged in an order that is thereverse of a sequence used in the filter layer 19. In the arrangement ofFIG. 4, the filter layer 19 is arranged as a periodic sequence of red,green and blue filters, while the barrier 20 comprises a sequence ofcolumns of blue, green and red filters. The use of a reversed sequencein the barrier 20 is required in order to ensure that light of differentcolours emerge from the display panel at the same angle. If the filterlayer 19 and barrier 20 used the same sequence of colour filters, thelight from the red, green and blue subpixels would follow differentdirections, and would create their own respective viewing zones.

In this particular embodiment, in order to avoid generating cross-talk,the width w of each column of the barrier 20 is equal to 2p, that is,twice the pitch of the subpixels. If required, the columns may beconfigured with a smaller width w, or a slightly larger width w, as willbe described in relation to other embodiments of the invention.

In this particular example, the filter layer 19 and barrier 20 arearranged so that the filter in each column does not match the colour ofthe subpixels that it overlies. However, it is not essential for thefilter layer 19 and barrier 20 to be arranged in this manner. In otherarrangements according to the invention, a number of overlying portionsof the filter layer 18 and barrier 20 may match in colour.

The barrier 20 may be manufactured using photolithography to formcolumns of photopolymer material, in which a pigment of the relevantcolour is dispersed. The red, green and blue columns may be, not is notnecessarily, formed of the same colour filter material as thecorresponding filters in the filter layer 19.

In order to avoid cross-talk, the red, green and blue filters used inthe filter layer 19 and barrier 20 should be configured so that thetranslucent spectra of the various colour filters do not overlap. Inthis case, light emerging from the layer 16 of electro-optically activematerial can only pass through areas in the filter layer 19 and barrier20 which match in colour. In other words, light cannot pass through acolumn of a given colour in the barrier 20 unless it has previouslypassed through a filter of the same colour in the filter layer 19. Thislimits the directions in which light emerges from the display as shownin FIG. 6, where light passing through green filters 19 b, 19 e in thefilter layer 18 passes through a green column 20 b of the barrier 20.However, the green column 20 b will block light emerging from the redand blue filters 19 a, 19 c, 19 d, 19 f.

The selective transmission of light through the barrier 20 and,therefore, the avoidance of cross-talk, can be facilitated by using abacklight 15 that emits light of well determined wave-length. One way inwhich this can be achieved is by using a backlight comprising aplurality of light emitting diodes (LEDs). As the spectra of red, greenand blue LEDs are well separated, the construction of one or more colourfilters that transmit light produced by an LED of a particular colourand not the others is relatively straightforward.

Referring again to FIG. 6, light emerging from the green filter 19 bpasses through column 20 b creates the right viewing zone 23. At thesame time, light from another green filter 19 e passes through the samecolumn 20 b and creates the left viewing zone 24, indicated using dashedlines. As the barrier 20 restricts the directions in which lightemerging from subpixels 19 b, 19 e can propagate, an intervening region25 located between the viewing zones 22, 23 is free from cross-talk.

The provision of a black matrix 22 results in the size of theintervening region 25 being increased and further reduces, or prevents,cross-talk.

FIG. 7 depicts a barrier 26 without a black matrix comprising a seriesof columns of red, green and blue filter material. It is noted that, inpractice, there may be a black matrix separating the filters that hasnegligible effect on the performance of the barrier 26. FIG. 8 depictsthe viewing zones 23′, 24′ and an intervening region 25′ produced by adisplay comprising the barrier 26 and a filter layer 27 where, like thebarrier 26, the filter layer 27 does not comprise a black matrix ofsignificant width. The size of the intervening region 25′ is limited bythe dimensions of the column 26 a in the barrier 26. In this particularexample, the barrier 26 is configured with columns 26 a with a width wthat is equal to, or less than, twice the pitch p of the subpixels. Fora typical subpixel size of 99 μm, the column pitch would be, at most,198 μm.

The formation of an additional viewing zone 28 is also shown in FIG. 8.In this figure, light passing through red filters 27 b and 27 c areshown proceeding through a red column 26 a of the barrier 26 to formleft and right viewing zones 23′, 24′ as previously described. However,light from the red subpixels may also pass through other red columns ofthe barrier 26 to create further viewing zones. An example of this isshown where light emerging from red filter 27 b also passes through redcolumn 26 b, as indicated using dashed lines, to form the additionalviewing zone 28. Although not shown, a portion of the light passingthrough the red filter 27 c will also pass through red column 26 b, toform another viewing zone while light emerging from red filters 27 a and27 d will pass through the red columns 26 a, 26 b and so on. In thismanner, a number of additional viewing zones may be created through asingle column 26 a, 26 b of the barrier 26.

While the formation of additional viewing zones 28 has been discussed inrelation to the second embodiment, such side views may also be createdby the display of FIG. 4.

For the display of the first embodiment, the angles {tilde over (α)},{tilde over (β)} at which the main viewing zones 23, 24 begin and end,when measured within the substrate 17 with respect to normal, can becalculated as follows:

$\begin{matrix}{{\overset{\sim}{\alpha} = {\arctan\left( \frac{{6{jp}\; 2p} - \frac{b}{2} + \frac{w}{2}}{d} \right)}}{\overset{\sim}{\beta} = {\arctan\left( \frac{{6{jp}} + \frac{b}{2} - \frac{w}{2}}{d} \right)}}} & (1)\end{matrix}$

where w represents the width of a single column 20 a to 20 c, b is thewidth of the black matrix of the filter layer 19, p is the pitch of thesub-pixels 19 a to 19 f, d is the separation between the filter layer 19and barrier 20 which, in this case, is thickness of the sheet 22, and jdenotes the number of the column.

Where the substrate 17 is made of a glass with a refractive index n of1.5, the angles α, β at which the actual viewing zones 22, 23 begin andend, following refraction at the interface between the substrate 17 andair, are given by:α=max(−1,min(1,arcsin(1.5sin({tilde over (α)}))))β=max(−1,min(1,arcsin(1.5sin({tilde over (β)}))))  (2)

The min and max functions in the above equations are used to avoidcomplex angles due to total internal refraction.

The angles α, β are dependent on the transmission of the barrier 20 andfilter layer 19 as follows:

$\begin{matrix}{\vartheta = {\left( {\beta - \alpha} \right) = {\frac{p - b}{p}\frac{w}{6p}}}} & (3)\end{matrix}$

where the factor 6 is included since the transmission of each colorfilter is approximately ⅓ and the width w of the columns 20 a to 20 c istwice the pitch p of the subpixels 19 a to 19 f.

FIG. 9 depicts the relationship between the angles α, β and thetransmission of the filter layer 19 and barrier 20 for an embodiment inwhich d =0.7 mm, p =0.1 mm and b =0.025 mm. In this example, two pairsof viewing zones 23 and 24, 28 and 29 are created, if the transmissionis less than˜0.18. The first and third viewing zones 23, 28 contain thesame information. Similarly, identical information is presented in thesecond and fourth viewing zones 24, 29. The viewing zones 23, 24, 28, 29do not overlap and, therefore, cross-talk is prevented.

The size of the viewing zones 23, 24, 28, 29 is dependent on theseparation d between the filter layer 19 and barrier 20, so that adisplay in which the separation d is small will create relatively largeviewing zones. FIG. 10 depicts the relationship between the angles α, βand the separation d, for arrangements in which the column width w istwice the subpixel pitch p and the remaining parameters are unchanged.Where the separation d is 1 mm, six viewing zones are created 23, 24,28, 28′, 29, 29′, as indicated by the various symbols, each of whichindicate the angle at which a respective viewing zone begins and ends,that is, angles α and β respectively. If the thickness d is within arange of, say, 0.35 to 0.7 mm, four viewing zones 23, 24, 28, 28′, 29,29′ are created. If d is less than 0.35 mm, the display creates only twoviewing zones 23, 24. Although this lowest range in separation resultsin a small number of viewing zones, such a configuration is potentiallymost useful for displays for use in automotive applications where only alimited number of viewing zones may be required.

If the subpixel pitch p is decreased by a given factor, in other words,if the resolution is increased, the sizes of the viewing zones 23, 24may remain unchanged if the separation d, black matrix width b andcolumn width w are scaled by the same factor. Therefore, if smallersubpixels are used, for example, subpixels with a pitch p of 42 μm, thesizes of the viewing zones 23, 24 can be maintained if there is acorresponding reduction in the thickness d of the sheet 22 to a valueof:

$d = {{\frac{0.042}{0.1} \times 0.35} \approx {0.150\mspace{14mu}{mm}}}$

Referring again to FIGS. 7 and 8, in an arrangement where the barrier 26and filter layer 27 do not include a black matrix, or if the blackmatrix is of such dimension that it has only a negligible effect on theperformance of the display, the opening angle ? of the viewing zones 23,24 is:

$\begin{matrix}{\vartheta = {a\;{\sin\left( {\frac{1}{n}{\sin\left( {a\;{\tan\left( \frac{3p}{d} \right)}} \right)}} \right)}}} & (6)\end{matrix}$

Therefore, the separation d required in order to obtain two viewingzones with opening angles ? of at least 20° is:

$\begin{matrix}{d < {\frac{p}{0.0781}.}} & (7)\end{matrix}$

For an arrangement in which the pitch p of the subpixels is 42 μm, theseparation d should be less than or equal to 0.538 mm.

As noted above, in known LCDS, the substrate 17 has a thickness of 0.7mm or 1.1 mm. In order to obtain the desired viewing zones, the sheet 22located between the layer 16 of electro-optically active material andthe barrier 20 must be relatively thin. A suitable structure can beobtained as follows.

With reference to FIG. 4, a barrier 20 is created by depositing colourfilter material and, if required, a black matrix, onto a substrate 17.Where the filter material is a photopolymer, this may be achieved usinga photolithographic method to form columns of the colour filtermaterials. The substrate 17 may be a conventional substrate for use inan LCD, with a thickness of 0.7 mm or 1.1 mm. A thin sheet 22 oftransparent material, such as glass, quartz or a light transmissiveplastic, is then placed on top of the barrier 20. In this example, thesheet 22 has a thickness of approximately 150 μm. The filter layer 19 isthen formed on top of the sheet 22. The filter layer 19 may be formedusing a similar photolithographic method to that used for the barrier20. The filter layer 19 may, if required, comprise a black matrix.

FIG. 11 depicts a third embodiment of the invention. Instead of beingpositioned in front of the filter layer 18, as in the first and secondembodiments, the barrier 20 is positioned between the backlight 15 andthe layer 16 of electro-optically active material. Such a barrier 20 iscreated by depositing colour filter material and, if required, a blackmatrix, onto a substrate 18 in a similar manner to that described above.The substrate 18 may be a conventional substrate for use in an LCD. Athin sheet 22 a of transparent material is placed on top of the barrier20. Means for operating the layer 16 of electro-optically activematerial, such as arrays of electrodes and TFTs, shown generally at 16a, are then provided on the sheet 22 a.

Due to the presence of the barrier 20, light incident on the layer 16 ofelectro-optically active material can only pass through the subpixels incertain, predetermined, directions. FIG. 11 depicts the passage of lightthrough one column 20 a and two filters 18 a, 18 e, where the column 20a and filters 18 b, 18 e are of matching colour. As a result, two views23, 24 are created, with an intervening region 25 in which there is nocross-talk.

In this particular embodiment, it is advantageous for the columns of thebarrier 20 to be cholesteric filters. As cholesteric filters have lightreflecting properties, this can result in improved light efficiency forthe display, since the light blocked by each column 20 a can bereflected into the back-light 15 for re-use.

The relationships between the angles at which the viewing zones startand end, α and β respectively, and the separation d between the barrier20 and filter layer 19, width w of the columns 20 a, subpixel pitch pand black matrix width b are as described above, in relation to thefirst and second embodiments.

Each of the above embodiments produce a symmetrical arrangement ofviewing zones 23, 24. However, in some applications, an asymmetricalarrangement of viewing zones 23, 24 may be desirable. For example, in anautomotive application, it may be preferable for the display to berotated towards a driver. This can be achieved by configuring a displaywith a suitable alignment of the columns 20 a to 20 c of the barrier 20relative and the filters 19 a to 19 f of the filter layer 19 that matchin colour. An asymmetrical arrangement may be based on any of the aboveembodiments. FIG. 12 depicts a filter layer 19 and barrier 20 for amulti-view display according to a fourth embodiment of the invention,which is arranged to provide such an assymetrical arrangement of viewingzones 23, 24.

FIG. 13 shows a multi-view display according to a fifth embodiment ofthe invention, arranged to provide two views. The display comprises abacklight 15, a display panel 14 and a lenticular screen 30. Thebacklight 15 is arranged to output collimated light. However, in analternative embodiment, the backlight may instead be arranged to emitlight lines.

The lenticular screen 30 is positioned between the backlight 15 anddisplay panel 14 and focuses the light from the backlight 15 so that thedisplay panel 14 is illuminated by a plurality of light lines. The pitchP of the lenses of the lenticular screen 30 is twice the pitch p of thesubpixels. In this particular embodiment, the pitch p of the subpixelsis 0.15 mm and the pitch P of the lenses of the lenticular screen 30 is0.3 mm. The thickness t of the substrate 18 that separates thelenticular screen 30 from the layer 16 of electro-optically activematerial is 0.7 mm.

The filter layer 31 used in the display panel 14 is shown in plan viewin FIG. 14. The positions of four columns of underlying columns ofsubpixels 32 a to 32 d are also indicated. The filter layer 31 isconfigured so that, when the display is in use, the filters are arrangedas a series of horizontal rows. Alternative subpixel columns are used topresent each view, so that subpixel columns 32 a and 32 c displayinformation to the first viewing zone 23, while subpixel columns 32 band 32 d display information for the second viewing zone 24.

FIG. 13 depicts light rays passing through one of the lenses 30 a of thelenticular screen 30. The lens 30 a images a light line onto thesubpixels, so that a light ray passing through one subpixel column 32 ais directed towards the first viewing zone 23 and light rays passingthrough another subpixel column 32 f is directed towards the secondviewing zone 24. The subpixel column 32 b, which is adjacent to subpixelcolumn 32 a is illuminated by light imaged by lens 30 b, as shown usingdashed lines. The next subpixel column 32 c, which is adjacent to 32 b,is illuminated by light imaged by lens 30 c. In this manner, adjacentsubpixel columns 32 a, 32 b, 32 c, 32 f are illuminated by light thathas passed through different lenses 30 a, 30 b, 30 c of the lenticularscreen 30. The light passing through subpixel column 32 a and itsadjacent subpixel column 32 b propagate along different directions,according to the viewing zone 23, 24 in which the information displayedin the subpixel column 32 a, 32 b is to be viewed.

The multi-view display of FIG. 13 also creates a number of cross-talkregions 25, 33, 34. One cross-talk region 25, located between theviewing zones 23, 24, is caused by the finite spotsize s of the lightpassing through the display panel 14.

Cross-talk regions 33, 34 are formed at the outside edges of the viewingzones 23, 24 and are caused by stray light. In cross-talk region 34,which is adjacent to viewing zone 24, a viewer can perceive light isthat has passed through subpixels 32 displaying information for theother viewing zone 23. This is indicated by the dotted line in FIG. 13,which shows light from lens 30 a passing through subpixels 32 g that areadjacent to the subpixels 32 f. The stray light is directed towards thethe second viewing zone 24. The subpixels 32 g display informationintended for the first viewing zone 23. Therefore, the stray light willresult in the display of information for the first viewing zone 23 inthe cross-talk region 34. Similarly, in cross-talk region 33, theinformation visible in viewing zone 23 is visible, together with lightthat has through subpixels 32 displaying information intended forviewing zone 24, as indicated by the other dotted line in FIG. 13.

The size of the viewing zones 23, 24 depends on the opening angle of thelight lines produced by the backlight 15 and lenticular screen 30, sothat an arrangement in which light lines with a relatively small openingangle creates viewing zones 23, 24 of reduced size. Meanwhile, the sizesof the cross-talk regions 25, 33, 34 are determined by the width of thelight lines. The maximum useable viewing angle f , which includes theviewing zones 23, 24 and cross-talk region 25, is determined by thethicknesses t of the substrates 17, 18 and the pitch p of the subpixels.In an arrangement where the thicknesses t of the substrates 17, 18 is0.7 mm and that the pixels are oriented as shown in FIG. 13, the maximumusable viewing angle f is 72°. If the width of the light line is 100 μm,the cross-talk region 25 has an opening angle ?′ of 24° and the viewingszones 23, 24 each have opening angles ? of 24°. However, by selectingsuitable dimensions for the light lines and lenticular screen 30,viewing zones 23, 24 with opening angles ? of 30° may be achieved.

While the viewing zones 23, 24 created by the display of FIG. 13 arerelatively large when compared with prior art displays, significantcross-talk regions 25, 33, 34, are also created. In a multi-view displayaccording to a sixth embodiment, shown in FIG. 15, cross-talk is avoidedby preventing the information presented on the display from beingvisible in regions 25, 33, 34.

In the display shown in FIG. 15, a backlight 35 is arranged to emitlight lines, for example, using a plurality of suitably configured lightsources and/or using a mask. The light lines have a pitch l that isapproximately twice the pitch p of the subpixels. A lenticular screen 30is positioned between the backlight 35 and the display panel 14. Inorder to simplify this figure, the layer 16 of electro-optically activematerial is not shown. In this figure, the positions of subpixels 32 areindicated by the positions of their corresponding filters in the filterlayer 31.

Due to the alignment between the lenses 30 a, 30 b and light lines shownin FIG. 15, the problems caused by the finite spot size s of lightimaged by the lenses in the arrangement of FIG. 13 do not arise.Therefore, no central cross-talk region 25 is produced.

The pitch P of the lenticular screen 30 is approximately equal to thepitch l of the light lines produced by the backlight 35. The lenses arepositioned between the light lines and configured with an appropriatestrength to focus the light lines onto the subpixels. The width of alight line when imaged onto a subpixel is preferably less than the pixelpitch p, in order to avoid unintentional illumination of adjacentsubpixels and therefore avoiding the formation of cross-talk regions atthe edges of the viewing zones 23, 24.

As in the display of FIG. 14, adjacent subpixels are illuminated bylight imaged by different lenses of the lenticular screen 30 thatpropagate in different directions corresponding to the viewing zone 23,24 in which the respective subpixels display information.

Where the substrates 17, 18 have a glass thickness of 0.7 mm, themulti-view display creates viewing zones 23, 24 with a viewing angle ?of 30°. The viewing zones 23, 24 are separated by an intervening region25 in which there is no cross-talk. The paths of light rays through thedisplay of FIG. 15, in order to display information from two respectivesubpixels, are shown in FIG. 16. The shaded region on the leftcorresponds to light rays for displaying information in viewing zone 24and the shaded region on the right corresponds to the equivalent lightrays for viewing zone 23.

In the multi-view display of FIG. 15, each light line is focused onto asubpixel that is adjacent to the lens of the lenticular screen 30 thatperforms said focussing. For example, a light line focused by lens 30 ais imaged on a subpixel 32 a while a light line focused by lens 30 b isimaged onto subpixel 15 b. It is not essential for the subpixels 32 a,32 b and lenses 30 a, 30 b to correspond to one another in this manner.Other configurations may be used in which each lens 30 a, 30 b focuseslight lines onto subpixels that not adjacent to it. In such anarrangement, the size of the intervening region 25, in which noinformation is visible, will be increased when compared with thatcreated by the multi-view display of FIG. 15.

Where the display panel 14 provides a large screen area, when comparedwith the distance between a viewer and the multi-view display, it may benecessary to apply a “view point correction” when configuring thedisplay. If the pitch P of the lenticular screen 30 and the pitch l ofthe light lines is twice the pitch p of the subpixels, a viewer may notbe able to see the whole of a displayed image from a single position. Aview point correction can be applied by using a lenticular screen 30 andlight lines with pitches P, l that are greater than twice the pitch p ofthe subpixels. The required adjustment to the pitches P, l of thelenticular screen and light lines would be less than 1%, that is, lessthan 0.02p. For example, a correction of approximately 0.002p may besufficient. Such a configuration allows the viewer to observe the wholedisplay. The principle of the view point correction can also be used tocreate viewing zones 23, 24 of a desired size by selecting appropriatepitches l, P for the light lines and lenticular screen 30.

Another technique for further improving he size of the viewing zoneswill now be described with reference to FIG. 17, which shows a dual viewdisplay according to a seventh embodiment of the invention. As in FIG.15, the layer 16 of electro-optically active material is not shown.

In the dual-view display of FIG. 15, an intervening region 25 is createdbetween the first and second viewing zones 23, 24, in which noinformation can be viewed. The first and second viewing zones 23, 24 canbe enlarged using a dedicated scatterer 36, placed in front of thedisplay panel 14 as shown in FIG. 17. This allows the presentation ofviewable information in the intervening region 25. This feature may beused instead of, or in addition to, optimizing the pitches l, P of thelight lines and lenticular screen 30 in order to create viewing zones23, 24 of a desired size.

In order to avoid cross-talk, the scatterer 36 should scatter incominglight over a limited range of angles that is less than, or equal to, theopening angle ?′ of the intervening region 25. In other words, thescattering profile should be relatively narrow. FIG. 18 a depicts anormal scattering profile. In a normal scatterer, a significant portionof the light is scattered over a wide angle, as shown by the “shoulders”of the profile. By way of contrast, the scatterer 36 has a scatteringprofile as shown in FIG. 17 b, where light is scattered over arelatively limited range of angles.

The scatterer 36 may be formed of a rough surface comprising a number offacets configured to provide a limited range of scattering angles. Anexample of a suitable structured scattering surface 38 is shown in FIG.18 a. FIG. 18 b depicts an example of an alternative scattering surface39, which is structured. It is not essential for a structured scatteringsurface to comprise sphere-like elements 39 a, 39 b and so on, as shown,however, whatever structures are provided should be of a small sizecompared to the pitch p of the subpixels, for example, with sizes of 10to 50 μm.

In an eighth embodiment of the invention, shown in FIG. 20, a multi-viewdisplay is configured so that it can be switched between a dual-viewmode and a single view mode. When operated in a dual-view mode, up tohalf of the subpixels can be seen by each viewer. In single view mode,all subpixels are visible to all viewers, in other words, the sameinformation is presented to each viewer.

In the display of FIG. 20, a diffuser 40 is located between thelenticular screen 30 and the layer 16 of electro-optically activematerial, not shown. The diffuser 40 is formed using a material whoselight transmission properties vary with the application of an electricfield thereto. For example, the diffuser 40 may be formed using apolymer dispersed liquid crystal (PDLC), which is transparent when anelectric field is applied but diffusive in the absence of an electricfield. Another suitable material for the diffuser 40 is a liquid crystalgel, which is normally transparent but becomes diffusive when a voltageis applied.

The diffuser 40 can be switched between at least two states by applyingan electric field. The electric field is provided by a voltage source 41and controlled using a switch 42. In its first state, the diffuser 40 istransparent so that the subpixels are illuminated by the light linesproduced by the backlight 35. The display produces multiple views in themanner described above in relation to the sixth embodiment. When thediffuser 40 is switched into a second state, it diffuses the light linesproduced by the backlight 36 so that the subpixels are uniformlyilluminated. The display produces a single view so that a viewer canperceive information displayed by all subpixels, regardless of whetherthey are positioned in the first or second viewing zones 23, 24 or theintervening region 25.

As noted above, in relation to prior arrangements, the problems ofcross-talk and viewing zones of limited size are due, in part, to thesmall pitch p of the subpixels relative to the separation d between abarrier and display panel. This separation d is often governed by thethickness t of a sheet of glass or similar material placed between thebarrier and display panel. This problem is overcome in a ninthembodiment of the invention, as will now be described.

In conventional multi-view displays, adjacent columns of subpixels of adisplay panel present information directed to different viewing zones.For example, if the filter layer 31 and underlying subpixels 32 shown inFIG. 14 were used in a known dual-view display, the first column ofsubpixels 32 a would display information for a first viewing zone whilethe second column of subpixels 32 b would display information for asecond viewing zone and so on. A number of embodiments will now bedescribed, which depart from this convention.

FIG. 21 depicts a portion of an array of subpixels, arranged in columns32 a to 32 d and so on, for use in a multi-view display in accordancewith a ninth embodiment of the invention, shown in FIG. 22.

In FIG. 21, the subpixels are marked ‘A’ or ‘B’ to indicate whether thesubpixels are to present information to a first or second viewing zone23, 24 respectively. The columns of ‘A’ subpixels 32 a, 32 b and ‘B’subpixels 32 d, 32 e are separated by intervening columns of subpixels32 c, 32 f, which remain switched off, or “dark”, while information isdisplayed for the viewing zones 23, 24.

In this particular embodiment, adjacent columns of subpixels are used topresent information to a given viewing zone. The subpixels in columns 32a and 32 b are arranged to present information to the first viewing zone23, while subpixels 32 d and 32 e are used to display information forthe second viewing zone 23.

In the display of FIG. 22, a rear barrier 43 comprising slits 44 ispositioned between the backlight 15 and display panel 14. The slits 44are aligned with the intervening columns 32 c, 32 f of dark pixels andhave a width w that is equal to the pitch p of the subpixels.

In this manner, the subpixel array acts as a second barrier, as lightcan pass through only the ‘A’ and ‘B’ subpixel columns 32 a, 32 b, 32 d,32 e. The presence of the intervening columns 32 c, 32 f preventcross-talk in the region 25 between the viewing zones 23, 24.

In this particular example, the width w of the slits 44 matches thepitch p of the subpixels 32. However, cross-talk can also be preventedin an alternative arrangement in which the slits 44 have a width w thatis less than the pitch p of the subpixels. The opening angles of theviewing zones 23, 24 depend on the width w of the slits 43, as well ason the separation d between the barrier 42 and the subpixels 32 and thenumber of views associated with each slit 44. If, however, the barrierincludes slits of a width w that is greater than the pitch p of thesubpixels, the resulting viewing zones 23, 24 will overlap, producingcross-talk.

The structure of a viewing zone 23′, in which information displayed bysubpixel columns 32 g and 32 h is visible, is shown in FIG. 22 usingdashed lines. Within the viewing zone 23′, there are regions in whichinformation from only one of the subpixel columns 32 g, 32 h is visible.These are labelled 23′a and 23′b respectively. Between these regions isan overlap zone 23′c, in which information displayed by both subpixelcolumns 32 g, 32 h can be viewed simultaneously.

For this particular example, where two adjacent subpixel columns 32 aand 32 b, 32 d and 32 e are used to present information for each viewingzone 23, 24 and the width w of the slits 44 is equal to the pitch p ofthe subpixels, the extent of the overlap zone 23′c can be calculated asfollows. The angles at which the overlap zone 23′c begins and ends aredenoted a and β respectively. However, before refraction at theinterface between the substrate 18 and air, the start and end angles aregiven by:

${\overset{\sim}{\alpha} = {\arctan\left( \frac{p}{d} \right)}};$$\overset{\sim}{\beta} = {\arctan\left( \frac{2p}{d} \right)}$

FIG. 23 is a graph showing the angles α and β, as a function of pld. Fora display in which the pitch p of the subpixels is 0.099 mm and theseparation d is 0.7 mm, a is equal to 12° and β is equal to 24°. Thus,the overlap zone 23′c has an opening angle ? of 12°.

A number of optional measures may be employed to increase the openingangle of the overlap zone 23′c. For example, in a tenth embodiment ofthe invention, a diffuser 45 can be placed in front of the display panel14, as shown in FIG. 24. If the diffuser 45 has an angular spread of,say, 10°, the improvement in the size of the overlap zone 23′c will beat the expense of the creation of a limited cross-talk region, some lossof resolution in the vertical direction and a reduction in the daylightcontrast of the display panel 14. However, if a diffuser 45 thatscatters only in the horizontal direction is provided, the loss ofvertical resolution may be reduced or avoided altogether. Furthermore, adiffuser 45 that scatters light in specific directions only, such asLumisty® foil produced by Madico, can be used. This type of diffuser istransparent for light with an incidence angle of ±15° with respect tonormal, but scatters light with an incidence angle outside this range.The use of this type of diffuser 35 results in less cross-talk than anormal diffuser, as well as a smaller reduction in the daylight contrastof the display panel 14. In any case, the presence of any type ofdiffuser 45 will enlarge the overlap zone 23′c. In addition, thepresence of a diffuser 45 will result in the subpixellation of displayedimages, arising from the use of only one third of the subpixels of thearray in providing a given view, to be less obvious to a viewer.

The sizes of the viewing zones 23, 24 and overlap zone 23′c can also beincreased by reducing the separation d between the barrier 43 and thesubpixels 32, for example, by decreasing the thickness of the substrate18.

A similar result can also be achieved by effectively producing lightlines at a position that is closer to the layer of electro-opticallyactive material, not shown. This concept is applied in a multi-viewdisplay according to an eleventh embodiment of the invention, shown inFIG. 25.

In this embodiment, a lenticular screen 46 is positioned between thebacklight 35, which is arranged to generate light lines, and thesubpixels 32. The lenticular screen 46 images the light lines at adistance c from the subpixels. The pitch P of the lenticular screen 46is equal to the pitch l of the light lines produced by the backlight 35.The lenticular screen 46 is positioned so that its lenses are alignedwith the light lines. In this example, the subpixels 32 are operated asshown in FIG. 21, so that the arrangement of ‘A’ subpixel columns 32 a,32 b, ‘B’ subpixel columns 32 d, 32 e and dark subpixel columns 32 c, 32e has a period of 6 subpixels. For this reason, the pitch of thelenticular screen 46 is six times the pitch p of the subpixels.

In this particular embodiment, the dark subpixel columns 32 c, 32 f arealigned with the light lines generated by the backlight 35, but it isnot essential for the dark subpixel columns 32 c, 32 f and light linesto be aligned in this manner. If the multi-view display is arranged toeliminate cross-talk in the intervening region 25, the width of thelight lines should be less than, or equal to, the pitch p of thesubpixels.

Since the pitch P of the lenses is six times the pitch p of thesubpixels, the maximum value of c is 5/11 of the thickness of thesubstrate 18. This effectively reduces the ratio of pld by a factor of5/11. For a subpixel pitch p of 0.099 mm, the effective pld ratio is0.064. Such an arrangement would provide an overlap zone 23′c in which ais 26° and β is 52°, in other words, having an opening angle ? of 26°.This compares favourably with the opening angle of 12° achieved by themulti-view display of FIG. 22.

Ideally, the opening angle of the light lines produced by the backlight35 is such that the light from a given light line passes through thelens it is aligned with. For example, to meet this requirement, lightfrom a light line produced at 35 b will pass through lens 46 b only andnot through adjacent lenses 46 a, 46 c. Therefore, in order to provide athin multi-view display, the opening angle of the light lines should besmall. In practice, the opening angle may be larger than the pitch of asingle lens 46 a. This results in light from a light line at 35 apassing through an adjacent lens 46 b and producing further, unwanted,light lines.

The problems caused by light lines with a large opening angle can beprevented by configuring the distance e between the backlight 35 andlenticular screen 46 such that the lenses 46 a to 46 d provide amagnification factor equal to a positive integer. An example of thisimaging is depicted in FIG. 26, which depicts the multi-view display ofFIG. 25, where the distance e between the backlight 35 and lenticularscreen 46 is such that the multiplication factor of the lenses 46 a to46 d is equal to one. This causes the light from a light line at 35 dentering an adjacent lens 46 c to be imaged at the same location as thelight from light lines at 35 b. In other words, the stray light isimaged at a distance c from the subpixels 32, at a position aligned withthe lens 46 b, the light lines from 32 b and, in this particularembodiment, an overlying column of dark subpixels 32 g.

When the array of subpixels is operated according to in FIG. 21, onlyone third of the subpixels are used to present a given view which, asnoted above, can lead to subpixellation of displayed images beingperceived by a viewer. Furthermore, this arrangement is not compatiblewith a conventional filter layout, in which the filters are arranged asa series of red, green and blue columns. This is because, within theoverlap zone 23′c, only two of the three available primary colours canbe viewed.

This problem can be overcome by using a specialized layout for thecolour filter layer 47. For example, the filters in the filter layer 47may be arranged as a plurality of horizontal rows, rather than verticalcolumns or as a two dimensional array of colour filters. In eitherarrangement, the light from different subpixels in a single column 32 amay pass through different colour filters, so that the informationvisible in the overlap zone 23′c comprises all of the available primarycolours. Another option would be to use a filter layer 47 with adifferent number of primary colours. For example, if the filter layer 47is arranged as a series of columns of red, green, blue and yellowfilters, there is no incompatibility between the filter layer andsubpixel arrangement.

In embodiments comprising a barrier, such as that shown in FIG. 22,another possible solution would be to position the filter layer 47 at anangle to the barrier 43, although this may result in the generation ofsome cross-talk. For example, the filter layer 47 and barrier 43 may bearranged so that the angle between them has a tangent of ⅓, that is, isapproximately 18.4°, by arranging one or both of the filter layer 47 andbarrier 43 at an angle to the subpixel array.

The above discussion assumes that the light lines emerging from theslits 44 has an opening angle that is less than or equal to 6p, that is,within one period of the arrangement of subpixels shown in FIG. 21. Inpractice, the angular spread of the light may be larger, though thiswill result in the duplication of viewing zones 23, 24. For example,FIG. 22 depicts two light rays, shown using dot-dashed lines, passingthrough subpixels 32 i, 32 j. This will result in a further viewingzone, not shown, in which the information shown in viewing zone 23 isduplicated.

FIG. 27 depicts an alternative arrangement of subpixels for use in amulti-view display according to a twelfth embodiment of the invention.In other words, column 32 a is used to present information to the firstviewing zone 23, while column 32 c is used to display information forviewing in the second viewing zone 24. Columns 32 b, 32 d, which arelocated between the ‘A’ subpixels, such as column 32 a, and ‘B’subpixels, such as column 32 c, remain switched off when the multi-viewdisplay is in use. While this arrangement has an effective pitch equalto the pitch p of the subpixels, the presence of the dark subpixels 32b, 32 d act to suppress cross-talk.

FIG. 28 shows a multi-view display comprising a subpixel array operatedaccording to FIG. 27. In this particular example, the slits 43 have awidth w that is equal to the pitch p of the subpixels. The multi-viewdisplay creates two viewing zones 23, 24, with an intervening region 25in which there is no cross-talk.

While the multi-view display of FIG. 28 reduces or prevents cross-talk,the resolution of the display panel 14 is reduced as only one out ofevery four subpixels 32 is used to provide a given view. In addition,the light efficiency of the multi-view display is reduced as alternatecolumns 32 b, 32 d of the subpixel array are switched off.

FIG. 29 depicts a subpixel array for use in a multi-view displayaccording to an thirteenth embodiment of the invention. In thisarrangement, three adjacent columns 32 a, 32 b, 32 c of subpixels areused to present information to a first viewing zone and three columns 32e, 32 f, 32 g are used to display information to a second viewing zone.Intervening columns 32 d, 32 h are provided, which remain switched offwhile the multi-view display is in use. In such an embodiment, three outof every eight subpixels is used to display information to a givenviewing zone. Therefore, this embodiment has a greater light efficiencycompared with the ninth to twelfth embodiments and, in addition, permitsthe use of a conventional layout of red, green and blue colour filters.However, in this embodiment, and in further embodiments that use morethan three adjacent columns of pixels to provide a given view, there isa relatively large interval i between the columns used to provide aparticular view. In this particular example, this interval i extendsbetween columns 32 c and 32 i. This increased interval i may result invisual artifacts.

In the ninth to thirteenth embodiments discussed above, the subpixelseffectively act as a barrier, allowing light to pass through selectedsubpixels in order to prevent cross-talk and/or provide viewing zones23, 24 of increased size. As the arrangements of FIGS. 21, 27 and 29differ in terms of how the individual subpixel columns 32 a to 32 h areemployed, that is, whether a given subpixel column 32 a to 32 h is to beswitched on or off and, if switched on, which information is to bedisplayed. Therefore, a single multi-view display can be arranged toswitch between operational modes according to two or more of thesearrangements, or between one or more multi-view modes and a single viewmode, by operating the array of subpixels accordingly, wherecorresponding modifications are made to the rear barrier 43.

In this respect, the rear barrier 43 may be replaced by a switchablebarrier, such as a liquid crystal cell or other light shutter typedevice, to provide a display that can be switched between multi-view andsingle-view modes. A display comprising such a barrier, in the form of aliquid crystal cell 47. The liquid crystal cell 48 can be switched intoa first state, in which it acts in a similar manner to the barrier43.The pixels or subpixels of the cell 48 are operated to form lighttransmissive portions, shown using vertical lines, and dark portions,corresponding to the slits 44 and opaque portions of the barrier 43 inthe ninth embodiment. In this state, the display creates multipleviewing zones 23, 24 as described above. When switched into a secondstate, the cell 48 becomes largely or completely transparent. Thedisplay may then be used to present a single view, in which all thesubpixels 32 of the display panel 14 may be illuminated.

If required, the cell 48 and the filter layer 47 may be arranged at anangle to one another, as discussed above in relation to subpixelarrangements with a period of six columns.

The display may be arranged so that the arrangement of lighttransmissive portions and dark portions created when the cell 48 is inits first state can be altered by operating the cell 48 accordingly. Forexample, the display of FIG. 30 uses the arrangement of subpixels 32shown in FIG. 21, which has a period of six subpixels. The display canbe reconfigured to use an arrangement with a period of eight subpixelsby operating the subpixels 32 as shown in FIG. 29 and by operating thecell 48 to provide a barrier with an appropriate period. In this case,the cell 48 would be operated so that every fourth column of subpixels32 is light transmissive.

The ninth, tenth, twelfth and thirteenth embodiments described aboveeach include barriers 43, 48 positioned between the backlight 15 andsubpixels 32. However, the barriers 43, 48 in these arrangements mayinstead be placed in front of the subpixels 32. FIG. 31 shows an exampleof a display with a front barrier, according to a fourteenth embodimentof the invention. The display otherwise resembles that of the thirteenthembodiment, where the barrier is a liquid crystal cell 48 that can beswitched between a first state, in which only portions of the cell 48are light transmissive, for presentation of multiple views, and a secondstate in which the cell is mostly, or wholly, light transmissive, wherethe display is used to create a single view. As in the previousembodiments, if required, the barrier 48 and filter layer 47 may bearranged so that the light transmissive portions of the barrier 48 andthe filters in the filter layer 47 are slanted with respect to oneanother, so that light from a light line passing through a givensubpixel column 32 a to 32 g will then pass through two or more adjacentfilters of the filter layer, producing a view based on more than oneprimary colour.

The opening angle of the viewing zones 23, 24 or overlap zone 23′c ofthe tenth and eleventh embodiments may be further improved by providinga diffuser and/or a lenticular screen, as discussed above in relation tothe eleventh embodiment.

In the ninth to fourteenth embodiments, the subpixel array is operatedaccording to an arrangement with a period of six, four and eightsubpixels respectively, the principle of an arrangement in whichselected columns of the subpixel array remain dark can be used toprovide arrangements with other periods. Furthermore, it is notnecessary for the same number of subpixel columns to be used for eachview and the subpixel layouts of FIGS. 21, 27 and 29 can be departedfrom in order to provide an asymmetric display. For example, anarrangement in which one period includes three ‘A’ columns of subpixels,two ‘B’ columns of subpixels and two intervening columns could be used.

FIG. 32 depicts a display system according to the present invention. Thedisplay system comprises a multi-view display 49 according to any one ofthe first to third, fifth and subsequent embodiments, arranged to createtwo viewing zones 23, 24, in which is displayed information intended forviewers 50, 51. The display 49 includes, or is otherwise connected to, acontroller 52, arranged to operate the display panel 14. For example,where the display panel 14 comprises a layer 16 of liquid crystalmaterial controlled by an array of TFTs, the controller 52 will operatethe TFTs according to the image data to be displayed. If the display 49includes a switchable diffuser 36, the controller 52 may also controlthe voltage source 41 and switching means 42. Where the display 49comprises a switchable barrier, such as the liquid crystal cell 47described in relation to the fourteenth and fifteenth embodiments, thecontroller 52 may also control the cell 47, for example, using adedicated array of TFTs, to provide a barrier with a desiredconfiguration.

The image data is generated by or received by one or more data sources54. For example, the display system may be mounted in an automotivevehicle 53, as shown in FIG. 5, and one data source 54 may be aprocessor arranged to generate and present route planning information inthe viewing zone 23 associated with the driver 50. Alternatively, oradditionally, image data may be obtained from a data source 54 such as adigital versatile disc (DVD) player, a video compact disc (VCD) playeror a receiver arranged to receive video or audio-video signals via aterrestrial or satellite network, such as a television receiver or areceiver of video telephone calls. Another example of a suitable datasource 54 is a terminal arranged to connect to a computer network suchas the Internet.

If required, audio output means may be provided to present audio signalsrelating to the displayed information. The audio signals may be providedby the external source and/or the controller 52. For example, aloudspeaker 55 or an output configured to provide sound via one or moresets of headphones, not shown, may be provided.

FIG. 33 depicts another display system comprising a multi-view display56 according to the present invention. In this figure, the processor 52,data source 54 and audio output means 55 are not shown. In this example,the display 56 is arranged to create an asymmetric arrangement ofviewing zones 23, 24, so that viewing zone 23 is orientated towards oneviewer 50. For example, in an automotive application, the viewing zone23 may be directed so that the driver 50 may view said informationwithout taking their vision off the road. The creation of an asymmetricarrangement of viewing zones 23, 24 has been discussed in relation tothe fourth embodiment. However, a number of the other embodiments canalso be adapted to produce such an arrangement. For example, the first,second, ninth, tenth and twelfth to fifteenth embodiments may bemodified to produce asymmetrically distributed viewing zones 23, 24 byaligning the barrier 20, 26, 43, 47 and filter layer 19, 27, 41 in asuitable manner.

From reading the present disclosure, other variations and modificationswill be apparent to persons skilled in the art. Such variations andmodifications may involve equivalent and other features which arealready known in the design, manufacture and use of display devicescomprising liquid crystal display panels or other display panels andcomponent parts thereof and which may be used instead of or in additionto features already described herein.

In particular, the above embodiments are dual-view displays that aresuitable for use in automotive applications. The invention may be usedto provide more than two different views simultaneously. For example, asubpixel layout providing ‘A’, ‘B’, ‘C’ and ‘D’ views in a similarmanner to the ninth to thirteenth embodiments of the invention may beprovided. Furthermore, the invention is not limited to multi-viewdisplays for use in the automotive environment and can be used topresent different information to multiple viewers in other applicationswhere viewers are likely to remain within a given viewing zone. Theseother applications include displays in aircraft cabins, coaches, waitingrooms, lecture theatres and so on.

The features of the above embodiments have been described in relation tosubpixels of the display panel 14 and, in particular, their pitch p.However, a multi-view display according to any of the above embodimentsmay be configured so that the pitch of any light lines lenticularscreens or other parameters is instead based on the pitch p of pixels.This is particularly appropriate where the display panel 14 is amonochrome display.

As noted above, it is not necessary for the display panel 14 to be aliquid crystal device. Other display panels may also be used, which neednot be of the light shutter type. Suitable alternative display panelsinclude electrophoretic displays, electrochromic displays,electro-wetting displays and micromechanical displays, such asmicro-electro-mechanical systems (MEMS) displays. In arrangementscomprising front barriers, such as the first, second, fourth andfifteenth embodiments of the invention, the display panel 14 may be alight emissive display device, such as a cathode ray tube (CRT), anarray of light emitting diodes, an organic light emitting diode (OLED)display, a field emissive display (FED) and so on.

The features of described in relation to separate embodiments may becombined, if appropriate. For example, although the use of a dedicatedscatterer and a switchable diffuser and the configuration of viewingzones by selecting an appropriate pitch l for the light lines and alenticular screen have been described in respect of separateembodiments, these features may be used in combination to provide theirrespective advantages.

In the embodiments comprising a barrier, the width w of the slits of thebarrier need not be equal to the pitch p of the pixels or subpixelsmultiplied by a given positive integer. As described above, the width wmay be less than this value, in order to improve separation of theviewing zones, or even slightly larger, in order to effect a view pointcorrection or to obtain viewing zones of a desired size, as discussedabove in relation to selected embodiments of the invention.

Furthermore, the provision of a dedicated scatterer and a switchablediffuser, in order to allow the multi-view display to be switchedbetween multi-view and single view modes, has been discussed in relationto the seventh and eighth embodiments of the invention only. However,such a diffuser may be included in any of the other embodiments of theinvention, where appropriate. Furthermore, the switchable diffuser maybe operated to illuminate one area of the display panel with light linesfor multiple views while simultaneously providing uniform illuminationover another area of the display panel to provide a single view.

The use of a multi-view display to create an asymmetric arrangement ofviewing zones has been discussed in relation to the fourth embodimentonly. However, other embodiments described above may be arranged tocreate such an asymmetric arrangement. For example, in the second andthird embodiments may be modified, so that the colour barrier and filterlayer may be aligned to produce asymmetric viewing zones in a similarmanner to that shown in FIG. 12. Similarly, in arrangements based on theninth, tenth and twelfth to fifteenth embodiments of the invention, thebarrier and filter layer also be aligned in such a manner.

Although Claims have been formulated in this Application to particularcombinations of features, it should be understood that the scope of thedisclosure of the present invention also includes any novel features orany novel combination of features disclosed herein either explicitly orimplicitly or any generalisation thereof, whether or not it relates tothe same invention as presently claimed in any Claim and whether or notit mitigates any or all of the same technical problems as does thepresent invention. The Applicants hereby give notice that new Claims maybe formulated to such features and/or combinations of such featuresduring the prosecution of the present Application or of any furtherApplication derived therefrom.

1. A multi-view display configured to display two or more views directedto two or more respective viewing zones, comprising: a display panel,comprising a plurality of imaging units, and a plurality of colourfilters, wherein each of said colour filters is associated with one ofsaid imaging units, the colour filters being arranged according to afirst pitch and in a first sequence of colours; and a barrier includinga plurality of colour portions comprising colour filter material, thecolour portions being arranged according to a second pitch that issubstantially equal to twice the first pitch and in a second sequence ofcolours that corresponds to the first sequence of colours when reversedin order, wherein the barrier is positioned so that light exits thedisplay panel after passing through one of the colour portions and oneof said colour filters and the colour portions of the barrier areconfigured to cooperate with the colour filters to selectively directsaid light passing to the first and second viewing zones; and whereintranslucent spectra of the plurality of colour filters of the displaypanel are prevented from overlapping translucent spectra of theplurality of colour portions of the barrier.
 2. The multi-view displayaccording to claim 1, arranged so that said light passes through one ofsaid colour filters before passing through said one colour portion. 3.The multi-view display according to claim 1, arranged so that said lightpasses through said one colour portion before passing through one ofsaid colour filters.
 4. The multi-view display according to claim 3,wherein the colour filter material of the colour portions is acholesteric filter material.
 5. The multi-view display according toclaim 1, comprising a light source arranged to illuminate the imagingunits of the display panel.
 6. The multi-view display according to claim1, wherein barrier is spaced from the colour filters by a separationinterval that is less than p/0.0781, where p is the first pitch.
 7. Themulti-view display according to claim 1, wherein the colour portions ofsaid barrier are separated from one another by a black matrix.
 8. Themulti-view display according to claim 7, wherein the plurality of colourfilters are separated from one another by a black matrix.
 9. Themulti-view display according to claim 8, wherein the barrier is spacedfrom the colour filters by a separation interval that is less than 0.35mm.
 10. The multi-view display according to claim 1, wherein the colourportions of the barrier and the colour filters are aligned so that thelight exiting the display panel produces viewing zones that areasymmetrically arranged.
 11. The multi-view display according to claim1, wherein said light source comprises a plurality of light emittingdiodes, wherein at least two of said light emitting diodes areconfigured to emit light of first and second colours respectively. 12.The multi-view display according to claim 1, wherein said imaging unitsare light emissive devices.
 13. A display system comprising: amulti-view display according to claim 1; and audio output means arrangedto output audio signals corresponding to the information displayed inone or more of said viewing zones.
 14. The multi-view display accordingto claim 13, arranged to display information in an automotive vehicle.15. Use of a multi-view display according to claim 13 to displaydifferent information in different ones of said viewing zones.
 16. Amethod of manufacturing a multi-view display according to claim 2,comprising: providing said plurality of colour portions on a lighttransmissive substrate; placing a sheet of light transmissive materialover said plurality of colour portions; and providing the plurality ofcolour filters of the display panel on said sheet of light transmissivematerial.
 17. A method of manufacturing a multi-view display accordingto claim 3, comprising: providing said plurality of colour portions on alight transmissive substrate; placing a sheet of light transmissivematerial over said plurality of colour portions; and providing meansconfigured to control said imaging units on said sheet of lighttransmissive material.